Nelson Mandela smiled as his two youngest great-granddaughters tried unsuccessfully to blow out the nine large and two small candles on his birthday cake, and had to be helped by the older children.

Surrounded by his closest relatives yesterday, Madiba celebrated both his 92nd birthday and his 12th wedding anniversary at his Houghton home in Joburg.

Mandela family spokesman Sello Hatang said the former president had started off his day by receiving visits from old friends. These included former Zambian premier Kenneth Kaunda.

Later, his large group of grandchildren and great-grandchildren sang, "Happy birthday, dear granddad", with most of them wearing the distinctive T-shirts designed to mark the first UN Nelson Mandela International Day.

Many of the Mandelas had spent time earlier in the day volunteering at community projects before they arrived at his private birthday party.

Once they had finished singing, the children were joined in their applause by the man of the moment, who watched with amusement as the smallest girls did their best to blow out his candles.

Mandela and his wife, Graca Machel, were joined at the private celebration of their anniversary by his former wife Winnie Madikizela-Mandela.

Graca Machel told the BBC that Mandela "is very well... he is healthy and taking into account the kind of life he had, it is really heartening.

He is getting old, he is getting frail but he is absolutely healthy, full of life, spirits high".

Mandela was last seen in public before the World Cup final match at Soccer City on July 11.

"He is going to have a cake, his family will surround him... we will gather at home, we will sit around, give him a lot of love," said Machel.

Before the main party got under way in a marquee in the garden, prayers were said by various ministers of religion.

The occasion also marked a commemoration of the death of various family members.

Yesterday, President Jacob Zuma addressed thousands of villagers at Mandela's birthplace Mvezo, one of the poorest areas in the country.

Where once Mandela used to celebrate his birthday by throwing a feast for the village, now the villagers were urged to spend 67 minutes of their time helping each other.

"Madiba's 67 years of uninterrupted and selfless service to the people of South Africa and the world culminated in the birth of a new South Africa, united in diversity," said Zuma.

He paid homage to the Mvezo Royal Chief, Mandla Mandela, the grandson of the former president. The chief then presented Zuma with a bull.

More than 6 000 people attended the Mvezo celebrations. Zuma and other VIPs arrived in helicopters and expensive cars while ordinary people arrived on horseback or walked. Zuma called on South Africans to unify by drawing lessons from Mandela's legacy.

"One of the lessons that we must draw... is that we must work together to entrench unity and solidarity in our country."

The president said that the spirit of unity displayed during the World Cup showed that unity between people of different races was possible. South Africans were united and they worked together to achieve one goal.

"We urge a continuation of this spirit of African unity, love and friendship."

Zuma thanked all South Africans who dedicated 67 minutes to improve the lives of others.

He also promised the people of Mvezo that the government would construct a bridge which would link their area with Idutywa.

Tributes for Mandela poured in throughout the weekend.

UN General Assembly president Ali Abdessalam Treki called Mandela "one of the greatest moral and political leaders of our time".

In the US, President Barack Obama spoke of Madiba's "extraordinary vision, leadership, and spirit".